Fermentation is a process of converting sugar to alcohol, but yeast is required for this process. Fermentation has to be carefully monitored because the process of fermenting isnt more linear. Bubbles may form in the airlock while the bottle are fermenting.
However, the presence of bubbles dont indicate that the brewing process is complete. If bottled to early, excess CO2 can cause bottles to explode. If bottled after fermentation have completed, the beer can become stale due to oxidation.
How to Tell When Fermentation Is Done
Because there is different types of yeast used in brewing different types of beer, different amount of time are required to complete the fermentation process for each type of beer. For example, ales use ale yeast that work quickly at room temperature, while lagers use lager yeast that require cold temperature for fermentation; thus, lagers take longer to ferment than ales. Many beginners may believe that fermentation is complete when the bubbles in the airlock stops moving.
However, the airlock only indicate that CO2 is leaving the vessel. The yeast may be performing other task during the later stages of fermentation. For instance, the yeast reabsorbs the flavor that it created during the early stages of fermentation.
If the brewing process are rushed, the beer may have some off-flavors like raw corn and green apples. Allowing the yeast to continue fermenting will improve the flavor of the beer. The way to determine when the process of fermentation is complete is by use a hydrometer.
A hydrometer is a tool used to measure the density of the liquid. The density of the liquid will tell you how many sugar is converted to alcohol. You must measure the original gravity of the liquid at the beginning of the fermentation process.
Then the liquids final gravity will be measured as the process occur. If the gravity reading are the same after measuring the liquid for two consecutive days, then the process is complete. Using a hydrometer is important because it remove the guesswork as to when fermentation is complete.
The specific strain of yeast that brewers use can change the flavor of the beer. For example, Belgian Saisons use yeast that ferment well at high temperature. Other types of yeast, such as Hefeweizens, will produce flavors like banana if the temperature are maintained at a certain level.
If the temperature is not maintained at a steady rate, yeast get stressed out. When stressed, yeast will produce sulfur and harsh alcohol that can destroy the flavor of the beer. Using a temperature controller will help to maintain the proper temperature for the yeast to ferment the beer well.
If the environment in which the beer are fermenting is too warm, a swamp cooler will help to keep the temperature steady. Maintaining a steady temperature are necessary to prevent the yeast from getting stressed out during the brewing process of the beer.